The worldwide HIV virus epidemic has caused respiratory diseases like tuberculosis, pneumonia and influenza also to increase in proportion after years of decrease. Sanitariums previously used for isolating patients with such diseases no longer exist or are very few. Existing hospitals are not well equipped for isolating the patient who has such a disease so as to prevent others from becoming infected. For example, the central heating, ventilating and air-conditioning (H.V.A.C.) systems of such hospitals are generally not designed to provide individual room negative air pressure and those systems that are, will often be old and may function improperly. Dedicating entire wards to these patients and retrofitting existing central H.V.A.C. systems is impractical, cost prohibitive and time consuming. The demographics of these diseases illustrate the largest need for isolation being in densely populated, low-income, urban areas where public health facilities require an especially cost effective method of isolation.
Various portable, patient isolation rooms and air-filtering systems have been developed for isolating patients with high susceptibility to infection. For example, U.S. Pat. Nos. 3,601,031 (Abel et al.) and 3,774,522 (Marsh) describe positive pressure rooms or enclosures which are designed and adapted to be assembled within an ordinary hospital room. Rooms with positive pressure not only allow air to escape but can actually force contaminated air treated by a contagious patient into adjoining rooms through cracks and crevices. Other portable structures, such as the one described in U.S. Pat. No. 4,928,581 (Jacobsen), provide negative pressure, but are constructed from softwall materials that can tear upon impact allowing significant pressure change, allow uncontrolled entry and exit and do not provide wall-mounted utilities within the protected environment.
Fan/filter units, such as those described in U.S. Pat. No. 4,917,713 (Helmus) and U.S. Pat. No. 4,560,395 (Davis), are commonly used in the clean room industry and are designed to provide positive pressure to a room at a manually controlled, fixed speed. However, because uniform air pressure across the filter is desired in clean room applications, internal baffles and chambers within their housings actually increase the surface area available for contaminated particle collection, prior to the filter, with no means of killing pathogens. Automatic compensation for opened doors, notification of pressure or power loss and entry/exit monitoring is also not an integral part or function of these units. Other fan/filter systems, such as that disclosed in U.S. Pat. No. 4,210,429 (Golstein) use high efficiency particulate air (HEPA) filters and germicidal lights to reduce infectious contaminants based upon the principle of recirculation within the room with no change in air pressure, or positive pressure. However, recirculation only creates turbulence within the room and allows contaminated air to escape when doors are opened.
There is a need for negative air pressure rooms that effectively isolate contagious patients and reduce the spread of disease, which can be readily assembled and disassembled within a preexisting structure and adapt to a wide variety of locations.